To get back on track...
Establishing the "group size" a rifle/optic/ammo combination is capable of is a matter of establishing mechanical process capability. The same thing is done in manufacturing processes. It's a matter of answering the question of exactly what level of precision a process is capable of.
Mathematically, this is approached by measuring variation from the mean. For rifles, the mean is the center of the group (and ideally the point of aim). Each shot is then measured as a distance from the center, with positive/negative x-y axes. From those distances, a standard deviation is calculated.
Six sigma is the general standard for establishing process capability. Each "sigma" is one standard deviation. Six sigma spans across the entire diameter of the group, so 3 sigma each way from the center in every direction.
These rules assume a "normal" distribution, which is a distribution that matches a standard bell curve. For rifles, that would mean nothing odd is going on with the optic, wind, or mechanical systems. Assuming there's no odd variables at play, this will result in a more or less perfectly round, circular group.
If the distribution is normal and the process is stable: 68% of the data fall within 1 standard deviation in any direction, 95% fall within 2 standard deviations in any direction, and 99.7% fall within 3 standard deviations in any direction.
A statistically verifiable 1 MOA rifle would be a rifle that put 99.7% of its rounds in a 1 MOA circle. 68% of its rounds would land in a much smaller circle, which is why so many 1 MOA rifles are listed as significantly better by their owners.
This is where confidence intervals and sample size come in. The more samples in the data, the higher the confidence that the standard deviation of the sample actually reflects the entire population. Samples of less than ten have low confidence. Going over 30 doesn't provide much more confidence. To say what we all already know, the number of shots in a group matters. Three shots over MOA means the rifle definitely isn't an MOA rifle, but three shots well under MOA doesn't guarantee that it is an MOA rifle.